In wireless communication systems, error-correction codes are used to introduce redundant bits in the transmitted packets in order to detect and correct errors in the transmitted packet at the receiver. In general, the more redundant bits introduced, the more error protection the code can provide. However, more redundancy implies that a larger transmission bandwidth is required or more delay will be incurred for transmission.
Thus, many wireless communication systems use Automatic Repeat Request (ARQ) schemes in conjunction with punctured error correction codes to transmit the minimal number of coded bits required to send an information packet without error. This is accomplished by removing some of the coded bits before the first transmission, to form a punctured packet for transmission. The removed coded bits are called punctured bits. If the transmitted packet contains errors that cannot be corrected, more punctured bits are transmitted. This may be repeated until an error-free information packet is decoded at the receiver.
There is a problem with transmitters now used in such systems for transmitting the information packets with incremental redundancy. These transmitters transmit the punctured bits over the same noisy channel as the previously transmitted punctured packet. This results in more requests for transmission of further coded bits than might otherwise be necessary, and thus reduced channel throughput.
Thus, there is a need for an improved wireless transmitter and method for transmitting incremental redundancy which does not use the same noisy channel as the previously transmitted punctured information packet.